a. Field of the Invention
The present invention relates to an air intake arrangement for an internal combustion engine.
b. Related Art
There are many factors that characterize the torque output of any given internal combustion engine, for example the swept volume within cylinders, cylinder configuration, the bore-to-stroke ratio, the compression ratio, valve train arrangement, and the inlet and exhaust arrangement.
Engine developers are constantly “tuning” engines, that is, adjusting these parameters and others in the search for improved fuel economy and performance. However, this does not necessarily result in increased power or torque as perceived by the driver. In real world driving conditions it is engine torque that is most important to the driver's perception of performance (or performance feel), and particularly engine torque delivered at lower engine speeds (rpm), for example, below 3500 rpm for a typical light duty passenger car application.
For this reason, an engine may need to be tuned to give higher torque at lower rpm, but this will typically result in a loss of torque at higher engine speed, for example an engine speed that is above about 3500 rpm. This is particularly a problem with small capacity gasoline engines, prevalent in the European marketplace.
The same engine could easily be ‘re-tuned’ to deliver the same torque but at much higher crank speeds. This results in significantly higher peak power but at the expense of torque at lower rpm. Whilst this will appeal to the ‘sporting’ driver, acceleration performance is reduced at lower engine speeds.
Engine designers have employed a multitude of techniques and technologies in an attempt to overcome this traditional compromise. Examples of such systems are variable geometry intake systems, variable camshaft timing and variable valve lift and timing. All of these approaches are designed to maintain more than one ‘state of tune’ depending on operating conditions.
Another commonly used technique is to reject engine tuning as a method for increased performance and instead pump air into the engine by means of a turbocharger or supercharger. Such forced induction generally results in significant increases in torque and power.
Such air compressors inevitably make some noise, and require cooling, particularly if the compressors are driven partly or entirely by an electric motor. This must be done in such a way that the space occupied by the compressor does not impinge unduly on other components near the engine. This is an increasingly difficult problem with modern motor cars, which are increasingly crowded under the hood or bonnet.
It is also important that an air compressor is inexpensive, if this is to be used with otherwise conventional, low capacity motor vehicle engines.